Deep-Sea Worms Can't Take the Heat

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Hot pink tube worms living on scalding deep-sea hydrothermal
vents actually like to keep things relatively cool, according to
a study published today (May 29) in the journal PLOS ONE.

Superheated water — at temperatures of more than 750 degrees
Fahrenheit (400 degrees Celsius) — spews from the vents. An
entire ecosystem clings to the chimneylike columns, with worms
and many other species consuming each other and the mineral-laden
hydrothermal fluids. Exploring the deep-sea
vents helps scientists determine the upper temperature limits
for life.

The fleshy pink Pompeii worm (Alvinella pompejana) is
one of the most extreme of the deep-sea creatures, perching its
long, bristly tubes right next to the shimmering vent fluids.
Earlier research had pegged the Pompeii worm's comfort zone
as high as 140 F (60 C), far beyond that of other animals.
But genetic and protein studies showed the worm's tissues would
unravel at such high temperatures, just like raw eggs change when
cooked. [ Life
at the Hydrothermal Seep (Video) ]

First worms alive on ship

Solving the riddle was tricky because until now, Pompeii worms
always died when brought to the surface. "The hottest animal on
the planet, but the most difficult to study, summarizes the
Alvinella enigma," said Bruce Shillito, a marine
biologist at the University Pierre and Marie Curie in France.

So researchers from the university built a special pressure
chamber for the worms to travel to the surface, to recreate the
intense pressures at deep
ocean vents. The team then tested heat extremes on the worms,
looking at survival and how much stress the different
temperatures caused. All of the experiments took place inside a
high-pressure aquarium aboard a research ship.

The
hydrothermal worms, from the East Pacific Rise,were given two
heat tests. Each lasted two hours. The first ramped up from 86 to
108 degrees F (30 to 42 C) and the second from 122 to 131 F (50
to 55 C). The scientists discovered that the Pompeii worms
survived the lower temperatures with no apparent tissue damage
and little heat stress. But within 10 minutes of the hotter test,
the worms crawled out of their tubes — an unnatural behavior —
and by the end of the test, all 18 worms were dead.

"This doesn't mean it cannot 'adventure out' in higher
temperatures, maybe 60 degrees Celsius, but then it would not be
permanent. A bit like you and I, who can stick our finger under a
tap with very hot water, but only for a few seconds. This same
water would certainly kill us if we had a bath," Shillito said.

The temperature results match up with experiments on related
hydrothermal
worm species taken from other deep-sea vents, said Ray Lee, a
marine biologist at Washington State University who was not
involved in the study. However, Lee said there could be other, as
yet unknown factors that help Pompeii worms survive hotter
temperatures in their deep-sea home. The handling and chemistry
changes during the trip to the surface could also affect how the
worms respond to the tests, he said.

"It's like you're taking them from outer space and putting them
on a shipboard lab," Lee said. "The major advance is that they
have eliminated the decompression factor, and that's one of the
hardest things to do."

Though the tests mean Pompeii worms like their homes a little
cooler than thought, the creatures are still one of the most
heat-tolerant animals on the planet. Shillito and his colleagues
now plan to examine the worm's tissues and genes to understand
how the animals thrive at the edge of hydrothermal vents.